Fluid absorbing, adhesive hydrocolloid compositions

ABSTRACT

A fluid-absorbing, composite material that is pressure sensitive adhesive and which is made of a mixture comprising a continuous phase formed from a pressure sensitive adhesive matrix, and a discontinuous phase substantially comprised of one or more natural or synthetically derived water soluble and/or water insoluble absorbents, characterised in that the continuous phase contains trans-polyoctenamer polymer, which material serves to elevate the shear strength of the composite. Because of its low melting point, compositions containing trans-polyoctenamer polymer are very easy to process. Formulations can be prepared that have only weakly adhesive properties, also formulations that are suitable as primary dressings for various hard-to-heal and chronic wounds. The pressure sensitive adhesive can also be combined with a non-adhesive, water impervious film, or other backing material, and can be used as the protective adhesive skin barrier component of ostomy pouches.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of International application numberPCT/GB00/03931, filed Oct. 13, 2000, which in turn claims priority ofBritish application number 9924374.3, filed Oct. 14, 1999, and Britishapplication number 9924375.0, filed Oct. 14, 1999.

This invention relates to a fluid-absorbing, composite material that ispressure-sensitive and comprises a continuous phase formed from apressure-sensitive adhesive matrix and a discontinuous phasesubstantially comprised of one or more natural or synthetically derivedwater soluble and/or water insoluble absorbents.

Pressure sensitive adhesive materials are used in many medical devicefields and are made into products such as tapes, bandages, surgicaldrapes, IV dressings and the like. Hydrocolloid pressure sensitiveadhesives are medically useful adhesives that have been known for about30 years and were originally developed as bandages for the oral cavityto aid in delivery of drugs to the gingiva. Hydrocolloid adhesives havebeen hitherto unique in that they are inherently adhesive and inherentlyabsorbent. They are useful as wound dressings because they can beapplied directly to open wounds and secured on the surrounding intactskin, and as skin barriers because they protect the peristomal skin ofostomy patients. Many hydrocolloid skin barriers are known and are usedfor these purposes. The more modern of these adhesives are “integrated”.In this context, “integrated” means those compositions thatsubstantially retain their dimensional stability and form when saturatedwith wound exudate and/or other body fluid. “Non-integrated” means thosecompositions which become soft gels and amorphous as they becomesaturated with fluid. The shear strength of both integrated andnon-integrated compositions can be improved using the teachings of thepresent invention, and the integrity of non-integrated compositions willalso generally be increased.

The first hydrocolloid compositions to be described were non-integrated.U.S. Pat. No. 3,339,546 discloses compositions which are inelastic, andwhich are non-integrated, i.e. which do not maintain their dimensionalstability and become amorphous when imbibed with wound fluid or otherbody fluid. A typical formulation taught by this prior art is thecomposition formed from low molecular weight polyisobutylene (40% bywt), pectin (20% by wt), sodium carboxymethyl cellulose (20% by wt) andgelatin (20% by wt). This formulation was used as a dressing for thegingiva but is also believed to be the basis of commercially successfulskin barrier and wound care products. Such compositions form a soft gelwhen in contact with an exuding wound, and the resultant gel remains inthe wound when the dressing is removed. This lack of integrity is adrawback. The gel must be removed from the wound at the time thedressing is changed. This is usually done by irrigation, which is timeconsuming for the nurse and painful for the patient. Adhesives taught bythis patent also normally have relatively low shear strength, which canbe a drawback in some use situations, particularly those in ostomy care,where the adhesive must retain on the abdomen a pouch containing bodywaste.

The lack of integrity was a serious drawback in the use of thesedressings and barriers and much development was completed in efforts toovercome the deficiency. Thus, British Patent 1,576,522 corresponding toU.S. Pat. No. 4,231,369, describes improved hydrocolloid compositionsthat are integrated. There is provided a sealing material for ostomy useconsisting of a hydrocolloid dispersed in a continuous phase ofstyrene-isoprene-styrene copolymer, or other thermoplastic elastomersuch as an ethylene-propylene copolymer. Also present is a hydrocarbontackifier and optionally an oil extender and an antioxidant. Thismaterial is said to have the advantage of being elastomeric andflexible. However, the absorption rate is lower than hydrocolloids madein accord with U.S. Pat. No. 3,339,546.

The shortcomings of barriers and dressings based upon formulae such asare described in U.S. Pat. No. 3,339,546 are also recognised by bothU.S. Pat. No. 4,477,325 and U.S. Pat. No. 4,738,257. These two laterpatents disclose barriers and dressings based on an integratedformulation containing a continuous phase composed of a blend of highvinyl acetate EVA copolymer (51% wt VA and 49% wt ethylene) and lowmolecular weight polyisobutylene, in which is dispersed a discontinuousphase containing a blend of a superabsorbent material, pectin and sodiumcarboxymethyl cellulose. The function of the EVA copolymer is to crosslink in the presence of ionising radiation, such as gamma radiation at adosage of, for example, 25 KGy, which would be used to sterilisedressings formed from the compositions of the invention. Thecross-linked network is formed essentially from the EVA polymer byirradiation of the EVA containing elastomeric phase. If the compositionis to be used as an ostomy barrier, the gamma radiation is an expensiveprocess to achieve integration, because ostomy products are not normallysold sterile. If the adhesive composition is used non-sterile, its shearstrength is low.

U.S. Pat. No. 4,551,490 describes integrated hydrocolloid adhesivesmodified by diluting the amount of styrene-isoprene-styrene blockcopolymer present in the composition. The patent provides a medicalgrade pressure sensitive adhesive composition comprising a heterogeneousmixture of one or more polyisobutylenes or blends of polyisobutylenesand butyl rubber, one or more styrene radial or block copolymers, atackifier, mineral oil and one or more water soluble and/or swellablehydrocolloid gums. It is believed that the polyisobutylenes, butylrubber, mineral oil and tackifier serve to modify and plasticisepredominantly the isoprene segment of the block/radial copolymer. Inparticular, the mineral oil is said to provide increased extensibilityand aggressiveness of the adhesive. It is believed that the teachings ofthis patent form the basis of the commercially available hydrocolloiddressing products DuoDerm and Signa Dress. However, it has been foundthat the rates of absorption of saline with these compositions is veryslow, and not very reproducible, and moreover very much less than theabsorption levels available with the compositions of U.S. Pat. No.3,339,546.

Our co-pending Application WO99/14282 describes a pressure sensitiveadhesive material made of a weakly elastic mixture comprising acontinuous phase formed from a blend of a physically cross-linked solidrubbers such as a styrene-isoprene-styrene triblock copolymer with astyrene-isoprene diblock copolymer, a compatible tackifying resin and alow molecular weight polyisobutylene, optionally modified by inclusionwithin the continuous phase of a quantity of butyl rubber, and adiscontinuous phase comprising one or more hydrocolloids that aresoluble and/or swellable in water. Small quantities of additives such asstabilisers and fumed silica may be present. The adhesive layer can becombined with a non-adhesive, water impervious film and can be used inwound care, ostomy care and in other medical products.

Our co-pending Application WO99/11728 describes a pressure sensitiveadhesive material made of an elastic mixture comprising a continuousphase formed from a physically cross-linked solid rubber such as astyrene-isoprene-styrene block copolymer, and a compatible liquidrubber, such as a liquid styrene-isoprene rubber, and a discontinuousphase comprised of one or more absorbents that are swellable or solublein water. Resinous materials are preferably absent, but additives suchas polybutenes, polyisobutylene, mineral oil, stabilisers, and otherrubbers, may be present. The pressure sensitive adhesives have theadvantage over the prior art that they are extremely well integrated andcontain no materials known to irritate skin and mucous membranes.

The composition of the present invention is characterised in that itcontains 0.1 to 50% by weight, based on the continuous phase oftrans-polyoctenamer.

The present invention provides compositions containingtrans-polyoctenamer polymer that overcome some of the problemsassociated with the prior art. The present hydrocolloid adhesives havedifferent and sometimes unique properties as compared to knownhydrocolloid adhesives. Compositions may be formulated within the scopeof the invention that have no leachable components that wouldcontaminate a healing wound, and they can be used in wound care, ostomycare and other medical products. Within the scope of the invention,formulations can be prepared that have only weakly adhesive properties,also formulations that are suitable as primary dressings for varioushard-to-heal and chronic wounds. By judicious choice of ingredientswithin the scope of the invention, compositions can be formulated thatare relatively clear or translucent, and so are able to allow a visualassessment of the healing progress and the condition of a wound under adressing.

One aspect of the present invention relates to barriers and wounddressings comprising a layer of absorbent adhesive coated on anon-adhesive, waterproof film. This construction is useful in a numberof ways. One of these is for bandaging purposes, especially on movablebody parts such as joints or on curved surfaces of the body. Wounds suchas blisters, burns, venostasis ulcers and decubitus ulcers mayadvantageously be treated with the products of the invention. Anotherimportant use is for the protection of the skin around body openings,especially around the surgically created openings known as colostomies,ileostomies and urostomies.

Another aspect of the invention comprises fluid absorbable pressuresensitive adhesives that contain an antimicrobial agent such as silversulfadiazine, quaternary ammonium compounds, povidone-iodine, and thelike. Such agents may be advantageously incorporated into theformulations of the instant invention to yield absorbent adhesives thatcan be made into dressings or pads for infected or colonised wounds.

A further aspect of the present invention comprises fluid absorbablepressure sensitive adhesives that are only weakly adhesive, and that maylose most of this low level of adhesion as the formulation absorbs forexample wound exudate. Such materials, formulated within the scope ofthe invention, are especially useful as pads for adhesive bandages anddressings, adhesive pads, surgical pads and the like. In thisembodiment, the materials would generally be held in place on the bodyby other pressure sensitive adhesives, and would function as an island,or central pad attached to one side, the wound contacting side, of acarrier or backing or fabric. In this embodiment, formulations areenvisaged that optionally may contain an effective amount of anantimicrobial or antibiotic substance.

Still another aspect of the present invention relates to integratedabsorbent pressure sensitive adhesives that are processable at lowertemperatures than prior art materials. The rubbery trans-polyoctenamerpolymer may be incorporated into the formulations of the instantinvention at relatively low temperatures, say at 80-90° C. Thethermoplastic elastomers of prior art integrated formulations must beprocessed at temperatures of at least 160° C., and preferably under anitrogen atmosphere, in order to melt the thermoplastic elastomer andplasticise it effectively. The trans-polyoctenamer polymer melts at muchlower temperatures. At these lower processing temperature, fewerunwanted side reactions or thermal and oxidative degradation occurs andlower quantities of processing stabilisers can be used. This in turnminimises the amounts of potential trace irritants and allergens in thefinished adhesive. Within the scope of the invention, thetrans-polyoctenamer may be advantageously incorporated with or withoutthe concomitant inclusion of other thermoplastic elastomers. The novelcompositions gain improved shear strength in either case, and improvedprocessability in the case where there is no accompanying additionalthermoplastic elastomer in the formulation.

A fluid absorbing composition according to the invention comprises acontinuous phase consisting of a mixture of a permanently tacky pressuresensitive adhesive and trans-polyoctenamer polymer and dispersed withinthe continuous phase a discontinuous phase of one or more water solubleand/or water swellable absorbent polymers.

The permanently tacky pressure sensitive adhesive component must betacky at room temperature as well as at the skin temperature ofpatients. Also, the adhesive must be dermatologically acceptable, whichmeans that after continuous contact with skin there is little adhesiveresidue upon removal and there is no significant reaction with the skinduring the adhesion period. The adhesive strength of the continuousphase must be sufficient to adhere to the skin of the patient for thetime determined by the use of the medical device of which the adhesiveforms part. Suitable permanently tacky pressure sensitive adhesivecomponents may be used singly or in admixture, and include naturalrubber, polyisobutylene, styrene-diene block copolymers,styrene-hydrogenated diene block copolymers, butyl rubber, acrylicpolymers, silicone rubber, polyurethane rubber, polyvinyl ether andother like substances.

Other ingredients such as tackifiers, plasticisers, and polymerstabilisers may be added to the continuous phase, to modify tack andoptimise adhesion properties and to protect polymers from degradationduring processing.

Trans-polyoctenamer is a crystalline metathesis polymer of cyclooctenewith predominantly trans-isomeric double bonds. It is said to contain amixture of linear polymer and macrocyclic groups within each polymerchain. The trans-polyoctenamer is exemplified by the materialsVestenamer 6213 and 8012, which are available from Hüls AG. The polymeras available from Hüls AG is said to contain 15% by weight of cyclicoligomers and 85% of acyclic polymer. The crystallinity of the polymeris thermally reversible and reforms very rapidly on cooling the polymerbelow its melting point. While the inventor does not wish to be bound byany particular theory of action, it is believed that the high ringcontent in the polymer chains serves to aid compatibility betweenotherwise incompatible elastomers. Also, the polymer crystallinity andthe high ring content increases the amount of network formation withinthe permanently tacky pressure sensitive adhesive continous phase.Further, the low content of double bonds in the polymer improves thethermal and oxidative stability of the formulation, while the lowviscosity of molten trans-polyoctenamer aids the processing of thesematerials. The trans-polyoctenamer is present in an amount correspondingto from 0.1% to 50% by weight of the continuous phase, preferably from3% to about 25% by weight of the continuous phase.

The discontinuous phase comprises one or more hydrophilic polymers thatare soluble or insoluble but swellable in water as themoisture-absorbing component. One or more swellable polymers may bepresent. Suitable insoluble swellable polymers include cross-linkedsodium carboxymethyl cellulose, crystalline sodium carboxymethylcellulose, cross-linked dextran and starch-acrylonitrile graftcopolymer. The swellable polymer may also be a so-called “superabsorbent” material such as starch sodium polyacrylate. Other hydratablepolymers such as gluten and polymers of methyl vinyl ether and maleicacid and derivatives thereof may also be included in the discontinuousphase. Suitable water soluble polymers include sodium carboxymethylcellulose, pectin, gelatine, guar gum, locust bean gum, collagen, karayagum and the like. The discontinuous phase should not normally exceed 70%of the total weight of the adhesive, and preferably does not exceed 60%by weight of the adhesive, and may be comprised of any combination ofsoluble and/or insoluble absorbents.

Optional fillers such as silica and pigments and optional activeingredients such as epidermal growth factors and antimicrobial compoundsmay also be incorporated into the compositions of the invention. Silversulfadiazine and benzalkonium chloride represent non-limiting examplesof such antimicrobial ingredients. Also essential oils such as, forexample, lavender oil or tea tree oil may be added in amounts sufficientfor efficacy. Other active ingredients such as those that provide awarming or cooling sensation to the skin, for example capsaicin ormenthol, may be added. Optional skin moisturising ingredients such asurea and polyols may be incorporated into the formulations of theinstant invention.

The adhesive compositions of the invention may be conveniently preparedas follows. The components of the continous phase such aspolyisobutylene, solid rubber, for example a styrene-olefin-styrenecopolymer and any liquid ingredients such as a liquid rubber or aplasticiser are blended together in a suitable mixer, normally a sigmablade or Z-blade mixer with an extruder discharge. If thermoplasticelastomers are used, the mixer will need to be heated to about 170° C. Anitrogen flow of about 60 ml/sec through the mixer reduces thepossibility of oxidative degradation of the rubber during processing.About 1 phr of a suitable stabiliser can be added at this stage. Afterblending of the rubbers, tackifiers, plasticisers etc. the mixer isusually cooled to 90-105° C. and the powdery ingredients are charged tothe mixer together with the other optional ingredients, if present, andblended in for a period of time, usually 20-30 min. If high molecularweight rubbers are used, they may need to be premasticated in the mixer,or premilled on a rubber mill. The fully mixed mass is then removed fromthe mixer and then extruded or pressed to the desired thickness, andthen laminated to suitable substrates.

The trans-polyoctenamer may be added to the contents of the mixer at theprepolymer stage, or later at the time the components of thediscontinuous phase are added. Since the trans-polyoctenamer melts atlow temperatures, it is very easily incorporated into the formulations.

Other processing techniques such as coating of the adhesive formulationsfrom a solvent slurry, may also be employed, especially if the desiredcoating weight is less than about 0.25 mm (250 μm). A general procedurefor this type of processing is given in U.S. Pat. No. 3,972,328, column2, ll. 44-60, and also in U.S. Pat. No. 4,427,737, column 2, ll. 24-47.Specific process procedures are given for each of the examples below.

Test Methods

The formulations prepared in the examples were evaluated using a numberof different test methods. Descriptions of these test methods follow.

Reverse Tack

Reverse tack of hydrocolloid adhesives is the maximum force necessary toremove a standard polyester strip brought into contact with thehydrocolloid without external force, from this hydrocolloid surface.

Procedure

Make the test panel self adhesive using double coated tape. Laminate thehydrocolloid adhesive on the test panel. Place the test panel withhydrocolloid in the lower clamp. Program the tensile tester. Place apolyester test strip of thickness 125 μm (5 mils) and dimensions (21cm×2.54 cm) in the upper clamp, making sure that the total length ofpolyester under the clamp (loop) is 15 cm. Remove the release liner fromhydrocolloid and start the measurement.

The reverse tack is the maximum force to remove the polyester strip fromthe hydrocolloid surface.

90° Peel Adhesion of Hydrocolloid Adhesives on Stainless Steel

Peel adhesion on stainless steel (SS) is the average force to remove ahydrocolloid adhesive, laminated under specified conditions on a SSpanel, from the SS panel at constant speed and at an angle of 90°.

Procedure

Clean the SS-panel with solvent. Cut a hydrocolloid sample of 25.4 mmwidth and reinforce with reinforcing tape, laminate a paper strip at oneend of the hydrocolloid sample using an overlap of about 1 cm. Removethe liner from the hydrocolloid sample and laminate the sample on theSS-panel with a 450 gm. roller at a speed of 150 cm/min. Allow thesample to dwell for 1 minute. Place the paper strip in the upper clampand the SS-panel on the lower clamp, making sure that the angle betweenpeel direction and SS-panel is 90°. Start the measurement using acrosshead speed of 300 mm/min. The angle must be kept 90° until themeasurement is completed. The 90° peel adhesion is the average force toremove the hydrocolloid strip from the SS-panel.

Static Shear of Hydrocolloid Adhesives

Static shear is the time necessary to remove a hydrocolloid adhesive,laminated on a stainless steel panel under specified conditions, fromthe test panel under influence of a specified weight.

Procedure

Condition the hydrocolloid samples at 23±1° and 50±2% relative humidityfor 24 hours. Clean the SS shear panel with solvent. Cut a hydrocolloidstrip of 25.4 mm width and 50 mm length. Reinforce the hydrocolloidstrip with reinforcing tape. Laminate the hydrocolloid strip on the testpanel using an overlap surface of 1 inch². Protect the free hydrocolloidwith release liner. Put a weight of 500 g on the laminate for 1 hour.Reinforce the free hydrocolloid adhesive zone with reinforcing plasticand perforate. Place the test panel with hydrocolloid on the shear barusing a shear weight of 500 g. Re-zero the registration-clock. Note thetime on the clock when the measurement is completed.

Static Absorption of Hydrocolloids

To determine the amount of fluid uptake into a known surface ofhydrocolloid adhesive.

Procedure

Laminate the double coated tape with release liner on the upper side ofthe cup (contact zone for hydrocolloid). Fill the cup with 30 ml NaClsolution (0.9% wt). Cut a sample of hydrocolloid of about the same sizeas the outer cup diameter. Weigh the sample (W₁). Laminate the sampleonto the cup, making sure that the seal between the hydrocolloid sampleand the cup is water tight. Turn the cup upside down and put it in theoven at 37° C. for 24 hours. Cool down. Remove the hydrocolloid from thecup and weigh (W₂). Calculate the water fluid absorption (g/sqm.24 h)with the formula:

abs=(W ₂−W₁)/0.002375

(surface contact zone salt solution/hydrocolloid=0.002375 sq. m)

Determination of Cold Flow

The flow of the hydrocolloid under influence of a specified pressure andafter a specified time, is measured.

Procedure

Condition the hydrocolloid samples at 23±1° C. and 50±2% relativehumidity for 24 hours. Cut 5 samples of hydrocolloid using a 35 mmcircular die-cutter Put a silicone paper on top of a first glass plate.Arrange the 5 samples on the silicone paper in a way that pressure isdistributed equally. Measure the diameter of each sample with callipers,mark the exact place where the measurement is done. Put a plastic diskon each sample. Put another silicone paper and two glass plates over theconstruction followed by a weight of 10 kg. After 24 hours, measure thediameter of the samples where they are marked. Calculate the % increaseof diameter of the samples. The cold flow is the % increase of diameterafter 24 hours exposure to 10 kg (for 5 samples).

Determination of the Intearity

The integrity of a hydrocolloid is defined as its ability to resistbreakdown by biological fluids. The test measures the weight percentageof hydrocolloid retained after exposure to saline under specifiedconditions.

Procedure

Condition the hydrocolloid samples at 23±1° C. and 50±2% relativehumidity for 24 hours. Cut circular samples from the hydrocolloid sheet2,54 cm diameter. Weigh and record the samples (W_(i)). Place eachsample in a 120 ml (4 oz) bottles with screw caps (Vel Catalog Number1198017) with 50 ml physiological saline (NaCl 0,9% wt in water), capthe bottles and agitate on a bottle shaker at 200 speed for a period of18 hrs. Remove the samples and dry them in the circulating air oven at50° C. and 50% relative humidity until dry. This usually takes about 24hours. Reweigh the sample (W_(f)). The Integrity Value of the sample iscalculated using the following equation:${{Integrity}\quad {Value}\quad (\%)} = {100 \times \frac{( W_{f} )}{( W_{i} )}}$

Note: The test may be run with hydrocolloid with or without carrier.However, the result may be affected, and suitable control samples shouldalways be included.

The invention will now be further described by reference to thefollowing non-limiting examples.

EXAMPLE 1-2

Examples 1 and 2 are hydrocolloid adhesives that comprisepolyisobutylene, Vistanex LMMH, available from Exxon Chemical Company,as the basis of the continuous phase. Three powdery ingredients comprisethe discontinuous phase; Genupectin USP100, available from HerculesChemical Company, Blanose sodium carboxymethyl cellulose 7H4XF availablefrom Aqualon Division of Hercules Chemical, and Gelatine 225 Bloomstrength, available from SKW Biosystems.

A laboratory Z-blade mixer was used to prepare the hydrocolloidcomposition of Example 1. The three powders were blended in the mixer at80° C., and the polyisobutylene was added to the powders and blended for20 minutes. Using the same procedure, another formulation was prepared,identical to that of Example 1, except that trans-polyoctenamer,Vestenamer 8012, was added at the end of the preparation, while thetemperature was maintained at 80° C. These materials had thecompositions set out in Table 1.

TABLE 1 Example Example Amount in mix, gm 1 2 Polyisobutylene, 203 203Vistanex LMMH Genupectin USP100 99 99 NaCMC Blanose 99 99 7H4XF Gelatine225 Bloom 99 99 Strength Vestenamer 8012 — 20 Total Weight, gm 500 520

The shear strength of Examples 1 and 2 were measured with the resultsshown in Table 2.

TABLE 2 Example Example 1 2 Shear 56 93 Strength, min

The data show that Vestenamer 8012, when incorporated in thehydrocolloid at 80° C. in the amount shown, increased the shear strengthto nearly double that without the Vestenamer 8012. These examples alsoclearly demonstrate the ease of incorporating the trans-polyoctenamer.It can be easily mixed into the formulation at the end of the processingcycle.

EXAMPLES 3-5

These examples utilise, as a basis, a continuous phase ofstyrene-isoprene thermoplastic elastomer, Kraton KD-1161N, tackifiedwith a mixture of Adtac LV-E and Escorez 2203 LC. The Kraton KD-1161N isa blend of linear styrene/isoprene/styrene triblock copolymer and linearstyrene/isoprene diblock copolymer. Such a material is available fromShell Chemical Company and has a bound styrene content of about 15% anda diblock content of 17%. The mixture of tackifying resins used was Oacyclopentadienyl resin, Escorez 2203LC, available from Exxon Chemical,and Adtac LV-E, a C5 synthetic hydrocarbon resin available from HerculesChemical Company. The polyisobutylene, Vistanex LMMH, is available fromExxon Chemical Company. The Irganox 1010 is a hindered phenolicantioxidant manufactured by Ciba.

A hydrocolloid adhesive, Example 3, was prepared as follows. Asigma-blade mixer was purged with nitrogen gas and heated to 160° C. Thespeed of the front, faster, blade was 47 rpm. The Kraton KD-1161N andthe Irganox 1010 were charged to the mixer at 160° C., and the mixer wasstarted. After mixing for 5 minutes, the rubbery crumb coalesced, andthe mixture of tackifying agents was added with continued mixing andnitrogen purging. After the tackifiers had completely mixed with therubber, the mixer was cooled to 105° C. and the polyisobutylene wasadded. After mixing for 10 minutes, the mixer was further cooled to 90°C. and the powdered ingredients were added. The total time for thisoperation was about 90 minutes. The finished hydrocolloid was removedfrom the mixture with a spatula and pressed between two sheets ofsilicone release paper in a hydraulic press with the platens maintainedat 90° C.

Examples 4 and 5 were made in a similar way, adding the Vestenamer 8012as the last ingredient at the end of the process. The results are shownin Table 3.

TABLE 3 3 4 5 Example No wt % wt % wt % Vistanex LMMH 28.0 28.0 28.0GenuPectin USP 100 14.0 14.0 14.0 Blanose 7H4XF 14.0 14.0 14.0 AqualonA500 14.0 14.0 14.0 Vestenamer 8012 — 5.0 10.0 Kraton D-1161NS 11.3 9.47.53 Adtac LV-E 6.0 5.0 4.0 Escorez 2203 LC 12.5 10.4 8.33 Irganox 10100.2 0.17 0.13 Total 100 100 100

The test results obtained on these formulations, compared to acommercially available hydrocolloid product from the 3M Company are setout in Table 4.

TABLE 4 3M Ex. 3 Ex. 4 Ex. 5 Hydrocolloid Reverse tack 34.6 21.3 18.814.0 N/in Peel 90° S.S. 17.2 10.4 4.2 9.9 N/in Shear 0.5 kg, 239 502 920141 min Thickness, mm 0.90 0.99 1.2 0.43 Static 7175 6998 6594 2545Absorption gm/m²/24hr Cold flow 4.0 1.6 0.7 0.7 23° C., %

The data show clearly that the products of the invention show improvedproperties over the 3M material and over example 3. For instance,Examples 4 and 5 have progressively improved shear strength, which isimportant for use of these adhesives as barriers for ostomy pouches.Examples 4 and 5 also have excellent cold flow performance, importantfor gentle removal of dressings from the often compromised skin aroundstomas, and for ensuring no transfer to the skin of adhesive that mayooze out from the edge of the adhesive barrier. Note that the Examples 4and 5 adhesives still possess higher tack than the product from 3M, andthat the absorbent capacity of compositions 4 and 5 of the invention arenot significant lower than that of Example 3, showing thattrans-polyoctenamer polymer has no deleterious effect on absorptioncapacity.

EXAMPLES 6-11

In a similar fashion to the above, examples 6-11 were prepared, with thecompositions shown in Table 5 below, and the products evaluated. Inthese examples, a lower molecular weight grade of trans-polyoctenamerpolymer, Vestenamer 6312 available from Hüls AG, was used in theformulations. The Vector 4111 is a 100% triblock S-I-S elastomeravailable from Exxon Chemical, the Regalite 101 is a syntheticcycloaliphatic resin available from Hercules Chemical Company, theIrgafos 168 is an organophosphite stabiliser available from Ciba and theIrganox 565 is a hindered phenolic antioxidant available from Ciba.

TABLE 5 Ex Ex Wt % Ex 6 Ex 7 Ex 8 Ex 9 10 11 Vistanex 26 26 26 26 26 26LMMH Pectin USP100 14 14 14 14 14 14 Blanose 14 14 14 14 14 14 7H4XFAqualon A500 14 14 14 14 14 14 Vestenamer — 5 10 — 5 10 6312 Kraton 12.010.1 8.28 — — — D-1161NS Adtac LV-E 6.4 5.4 4.4 5.78 4.88 3.98 Escorez13.3 11.2 9.16 — — — 2203 LC Irganox 1010 0.21 0.18 0.14 — — — Vector4111 — — — 11.5 9.73 *7.93 Regalite 101 — — — 14.4 12.1 9.92 Irgafos 168— — — 0.16 0.13 0.11 Irganox 565 — — — 0.08 0.07 0.06 Total, % 100 100100 100 100 100

The hydrocolloids were pressed to a uniform thickness of 0.82+/−0.06 mmin a platen press at 90° C. between two sheets of silicone coatedrelease paper, and the samples were tested with the results shown inTable 6.

TABLE 6 Ex Ex Ex 6 Ex 7 Ex 8 Ex 9 10 11 Sample 0.88 0.79 0.80 0.78 0.770.86 Thickness, mm Reverse Tack, 28.8 24.3 19.7 34.9 24.6 18.4 N/25 mmPeel Adhesion, 9.8 9.7 6.9 15.4 9.6 6.8 N/25 mm Shear Strength, 255 339456 327 461 576 min Cold Flow, % 4.3 1.5 0.8 2.7 1.4 — increase/24 hrStatic Absorp, 6598 6589 6055 6918 7133 7090 g/sq.m/24 hr Integrity, %60 77 61 61 66 73

The influence of the trans-polyoctenamer is very clearly seen in theseexamples. With increasing trans-polyoctenamer, 0, 5 and 10 wt %, thetack decreases slightly but uniformly, the peel adhesion decreases, theshear strength increases dramatically, the cold flow is greatlyimproved, the absorption level is unaffected and the integrity increasesmarginally.

The data also show the effect on shear strength of a mixed di- andtri-block styrene-isoprene elastomer. Examples 6-8 have a mixed di- andtri-block elastomer, while examples 9-11 are integrated with a 100%tri-block Exxon Vector 4111 material, and the improved shear strengthdue to the 100% tri-block elastomer is clearly seen and is entirely inaccord with expectation. But what is significant and unexpected is thatthe effect of the trans-polyoctenamer on shear strength is even morestriking.

EXAMPLE 12-13

These examples utilise a continuous phase of styrene-isoprenethermoplastic elastomer, Kraton KD-1161N, plasticised with astyrene-isoprene liquid rubber, LVSI-101. The Kraton KD-1161N is a blendof linear styrene/isoprene/styrene triblock copolymer and linearstyrene/isoprene diblock copolymer. This material is available fromShell Chemical Company and has a bound styrene content of about 15% anda diblock content of 17%. The LVSI-101 is a block copolymer of styreneand isoprene having a styrene content of about 13% and an isoprenecontent of about 87%, a glass transition of about −60° C., a meltviscosity of about 2400 poises at 50° C. and which is commerciallyavailable from Shell Chemical Company. The Irganox 1010 is a hinderedphenolic antioxidant manufactured by Ciba.

A Z-blade mixer was purged with nitrogen gas and heated to 160° C. Thespeed of the front, faster blade was 30 rpm. Kraton KD-1161N (100 gm)and Irganox 1010 stabiliser (4.0 gm) were charged to the mixer at 160°C., and the mixer was started. After mixing for 5 minutes, the rubberycrumb coalesced, and 50 gm of liquid rubber styrene-isoprene copolymer,LVSI-101, was added with continued mixing and nitrogen purging. After afurther ten minutes, the temperature was raised to 170° C. and the mixerfront blade speed increased to 47 rpm. The LVSI-101 had at this pointcompletely mixed with the rubber, and a further 50 gm of LVSI-101 wasadded. Ten minutes later, after blending of the second portion of theLVSI-101, a further 49 gm of LVSI-101 was added, and mixed for a further10 minutes. In this way, approximately 50 gm portions of the charge ofLVSI were added every 10 minutes until a total of 400 gm of LVSI-101 hadbeen added. After a further 15 minutes, the intermediate adhesive, withthe composition shown in Table 7, was dumped from the mixer. The totaltime for this operation was about 90 minutes.

TABLE 7 Formula 2-18A Gm. LVSI-101 400 Kraton KD- 100 1161N Irganox 10104

From this intermediate mixture, referred to as Formula No 2-18A in Table8 below, in which all weights are in grams, a finished hydrocolloid wasmade having the following formula. The Aquasorb A500 is crystallinesodium carboxymethyl cellulose available from Aqualon, Division ofHercules Chemical. The Aerosil 200 is fumed silica available fromDegussa AG.

TABLE 8 Example Vistanex Aquasorb Formula Aerosil No. LMMH A500 2-18A200 12 65.6 98.5 164.1 6.7

The mixer temperature was reduced to 90° C. and the absorbent powder andsilica was placed in the mixer and the mixer started. No nitrogen purgewas used in this phase of the preparation. The Vistanex LMMH was added,the temperature raised to 105° C., the mix blended for 10 minutes, afterwhich the intermediate adhesive, referred to as 2-18A in Table 8 above,was added. Blending was continued at 105° C. for a further 30 minutes,and the finished formulation was removed from the mixture with aspatula. The finished hydrocolloid was pressed between two sheets ofsilicone release paper in a hydraulic press with the platens maintainedat 90° C.

In a similar manner to the above, except that the Vestenamer 8012 wasincorporated into the Kraton KD-1161N prior to addition of the LVSI-101,an adhesive was prepared having the composition set out in Table 9.

TABLE 9 Formula No: Amount gm. 2-30A LVSI-101 400 Kraton KD-1161N 100Vestenamer 8012 20 Irganox 1010 4

From the above intermediate adhesive 2-30A, the following composition asshown in Table 10 was prepared as example 13. All weights in are grams:

TABLE 10 Example Vistanex Aquasorb Formula No. LMMH A500 2-30A 13 80 120200

The formulated adhesive was extruded at 100° C. on to a silicone coatedrelease paper, calendered down to a gauge of about 0.6 mm and laminatedto an acrylic adhesive coated polyurethane film. The acrylic adhesive onthe polyurethane film served as a tie coat to anchor the absorbentadhesive to the film. The results below in Table 11 show that theadhesive of Example 13 has twice the shear strength of that of Example12.

TABLE 11 Ex 12 Ex 13 Reverse tack N/in 12.3 23.2 Peel 90° S.S. N/in 5.010.2 Shear 0.5 kg, min 250 542 Thickness, mm 0.45 0.62 Static Absorption2021 3793 gm/m²/24 hr Cold flow 23° C., % 1.0 1.6

EXAMPLES 14 and 15

These examples show the use of an acrylic polymer as the basis of thepressure sensitive adhesive matrix. In the preparation of each examplethe acrylic polymer, available from BASF as AC Resin A258, was added tothe powdered absorbents in a Z-blade mixer at 90° C., and mixingcontinued until a homogeneous mixture was obtained. For example 15,trans-polyoctenamer, Vestenamer 6312, was added at the end of thepreparation, while the temperature was maintained at 80° C. In eachcase, the resultant hydrocolloids were pressed at 90° C. between twosheets of silicone coated release paper in a hydraulic upstroking platenpress to give sheets of material of about 0.8 mm in thickness. Thesematerials had the compositions and properties shown below in Tables 12Aand 12B.

TABLE 12A Amounts in gm: Ex. 14 Ex. 15 Acrylic AC Resin 290.2 180.0 A258Blanose 7H4XF 118.2 73.3 Pectin USP100 118.2 73.3 Aquasorb A500 118.273.3 Vestenamer 6312 — 44.4 Totals 554.8 444.3

TABLE 12B Ex. 14 Ex. 15 Integrity, %  7  55 Shear Strength, 56 155 min

The integrity and the shear strength of each adhesive were measured andthe influence of the trans-polyoctenamer, Vestenamer 6312 was assessedin this way. It can be clearly seen that the trans-polyoctenamerincreases both the integrity and the shear strength of the adhesive.

EXAMPLES 16-19

These examples show the incorporation of trans-polyoctenamer polymer ina hydrocolloid adhesive to produce low tack, low adhesion antimicrobialcontaining compositions, suitable for use as dressing pads for burns andother bacterially colonised wounds. In a similar fashion to theprocedure described in Examples 12 and 13, an intermediate adhesive (No:2-79A) was prepared as follows, with the composition shown in Table 13.

TABLE 13 Material gm Wt % Kraton KD-1161N 280.0 39.68 Irganox 1010 5.60.79 LVSI-101 420.0 59.52 Total 705.6 99.99

The Z-blade mixer was heated to 90° C. and the intermediate hot meltadhesive was added, and allowed to soften for 5 minutes. Then theAquasorb was added at 100° C., with continuation of mixing for a further15 minutes. After cooling to about 80° C., the antimicrobial additiveswere then added, followed by the Vestenamer 6213, and mixing wascontinued for 20 minutes, when the compounds were removed from the mixerand pressed at 90° C. between two sheets of silicone release paper. Thetack and adhesion of these compositions is very low, and they areparticularly suitable for application to wounds as dressing pads. Thefull compositions are set out in Table 14.

TABLE 14 Material, gm Ex 16 Ex 17 Ex 18 Ex 19 LVSI Hot Melt 280 280 280280 2-79A Vestenamer 120 120 120 120 6213 Aquasorb A500 120 120 120 120Tea Tree Oil 0 0 10.6 0 Benzalkonium 0 0 0 1.56 chloride* Silversulfadiazine 1.56 5.25 0 0 Total 521.56 525.25 530.60 521.56*N-alkyl-N,N-dimethyl-N-benzylammoniumchloride, available from LonzaSpecialty Chemicals

EXAMPLE 20

The adhesive compositions of the invention may include a skinmoisturizing agent.

This example describes the preparation of a moisturising adhesivecontaining a high proportion, 40 wt %, of glycerine, and containing 20wt % trans-polyoctenamer Vestenamer 6213 to give an adhesive whoseadhesion power decreased with time of wearing.

An integrated hydrocolloid adhesive was prepared in a Z-blade mixerusing LVSI-101, a liquid rubber component that is resin free, to tackifythe solid S-I-S rubber component.

Description of the ingredients used follows. The LVSI-101 is a blockcopolymer of styrene and isoprene having a styrene content of about 13%and an isoprene content of about 87%, a glass transition of about −60°C., a melt viscosity of about 2400 poises at 50° C. and which iscommercially available from Shell Chemical Company. The Kraton KD-1161NSis a blend of linear styrene/isoprene/styrene triblock copolymer andlinear styrene/isoprene diblock copolymer available from Shell ChemicalCompany- It has a bound styrene content of about 15% and a diblockcontent of 17%. Irganox 1010 is a hindered phenol antioxidantmanufactured by Ciba. The Aquasorb A500 is crystalline sodiumcarboxymethyl cellulose available from Aqualon, Division of HerculesChemical Company.

The mixer was purged with nitrogen gas and heated to 160° C. The speedof the front, faster, blade was 30 rpm. The Kraton KD-1161NS and theIrganox 1010 were charged to the mixer at 160° C., and the mixer wasstarted. After mixing for 5 minutes, the rubbery crumb coalesced, and2.5 kg of the LVSI-101 was added with continued mixing and nitrogenpurging. After a further ten minutes, the temperature was raised to 170°C. and the mixer front blade speed increased to 47 rpm. The LVSI had atthis point completely mixed with the rubber, and a further 2.5 kg ofLVSI was added. Ten minutes later, after blending of the second portionof the LVSI, a further 2.5 kg of LVSI was added, and mixed for a further10 minutes. In this way, approximately 2.5 kg portions of the charge ofLVSI were added every 10 minutes until all the 20 kg had been added. 15minutes later, the intermediate adhesive was dumped from the mixer. Thetotal time for this operation was about 90 minutes.

The mixer temperature was reduced to 90° C. and the absorbent AquasorbA500 powder was added to the mixer. No nitrogen purge was used in thisphase of the preparation. Blending was continued for a further 30minutes, and the finished formulation was removed from the mixer. Theintermediate hydrocolloid adhesive, 2-67A, had the composition set outin Table 15.

TABLE 15 Amounts in kg 2-67A Wt % LVSI-101 20.0 57.14 Kraton KD- 5.014.29 1161NS Irganox 1010 0.2 0.57 Aquasorb A500 9.8 28.00 Total 35.0100.00

This intermediate hydrocolloid adhesive 2-67A was further compounded at90° C. in a much smaller laboratory Z-blade mixer with glycerine, andtrans-polyoctenamer Vestemer 6213 in the proportions shown in Table 16.

TABLE 16 Wt % Gms 2-67A 40 200.0 Glycerine 40 200.1 Vestenamer 6213 20100.0 Total 100  500.1

Thus, the finished composition had the following composition shown inTable 17.

TABLE 17 Wt % LVSI-101 22.86 Kraton KD- 5.71 1161NS Irganox 1010 0.23Aquasorb 11.20 A500 Glycerine 40.00 Vestenamer 6213 20.00 Total 100.0

The formulated adhesive was pressed at 90° C. between two sheets ofsilicone coated release paper, and laminated to an acrylic adhesivecoated non-woven fabric commercially available from Avery DennisonSpecialty Tape Division, Turnhout, Belgium as MED1817. The acrylicadhesive on the non-woven fabric served as a tie coat to anchor thehydrocolloid adhesive to the non-woven fabric.

The composite adhesive laminate was cut into 2.5 cm×7.5 cm strips andwas wear tested on the calves of four female panelists. The adhesive wasinitially moderately adhesive to skin. As the glycerine was absorbedinto the skin, the composition became less tacky and less adhesive,causing the adhesive power to decrease with wearing time, and theadhesive to be only very weakly adhesive to the skin after about 8 hoursof wear. After removal of the adhesive, the underlying skin wasnoticeably softer to the touch than the surrounding skin.

What is claimed is:
 1. A pressure-sensitive adhesive compositioncomprising a continuous phase formed from a pressure-sensitive adhesivematrix and a discontinuous phase consisting essentially of one or morenatural or synthetically derived water soluble and/or water-insolubleabsorbents, characterised in that the composition contains 0.1 to 50% byweight, based on the continuous phase, of trans-polyoctenamer.
 2. Anadhesive composition according to claim 1 which is clear or translucent.3. An adhesive composition according to claim 1 or claim 2 wherein thediscontinuous phase constitutes not more that 70% by weight of the totalcomposition.
 4. An adhesive composition according to claim 3 wherein thediscontinuous phase constitutes not more than 60% by weight of the totalcomposition.
 5. An adhesive composition according to claim 1 which alsocontains an antimicrobial agent.
 6. An adhesive composition according toclaim 1 wherein the trans-polyoctenamer constitutes from 3 to 25% byweight of the continuous phase.
 7. An adhesive composition according toclaim 1 wherein the discontinuous phase contains one or more swellablepolymers.
 8. An adhesive composition according to claim 7 wherein thediscontinuous phase contains at least one swellable polymer selectedfrom cross-linked sodium carboxymethyl cellulose, crystallinecarboxymethyl cellulose, cross-linked dextran, starch-acrylonitrilegraft copolymer and starch sodium polyacrylate.
 9. An adhesivecomposition according to claim 1 wherein the discontinuous phasecontains at least one hydratable polymer selected from gluten, polymersof methylvinyl ether and maleic acid and derivatives thereof.
 10. Anadhesive composition according to claim 1 wherein the discontinuousphase contains at least one water-soluble polymer selected from sodiumcarboxymethyl cellulose, pectin, gelatin, guar gum, locust bean gum,collagen and karaya gum.
 11. An adhesive product comprising a layer of apressure sensitive adhesive composition according to claim 1 coated on abacking or carrier material.
 12. An adhesive product according to claim11 wherein the backing material comprises a non-adhesive waterprooffilm.
 13. An adhesive product according to claim 11 or claim 12 whereinthe adhesive composition includes a skin-moisturizing agent.
 14. Amethod of making an adhesive composition according to claim 1, whereinthe trans-polyoctenamer is incorporated into the other components of thecontinuous phase at a temperature not exceeding 100° C.